HR: 0800h
AN: H31D-0407    [Abstracts]
TI: Towards the field-scale experiments and numerical modeling of pesticides in tropical soils
AU: * Dusek, J
EM: dusek@mat.fsv.cvut.cz
AF: Czech Technical University, Faculty of Civil Engineering, Dept. of Hydraulics and Hydrology, Thakurova 7, Prague, 16629 Czech Republic
AU: Ray, C
AF: Water Resources Research Center, University of Hawaii at Manoa, 2540 Dole St., Holmes Hall 283 , Honolulu, HI 96822 United States
AU: Sanda, M
AF: Water Resources Research Center, University of Hawaii at Manoa, 2540 Dole St., Holmes Hall 283 , Honolulu, HI 96822 United States
AU: Vogel, T
AF: Czech Technical University, Faculty of Civil Engineering, Dept. of Hydraulics and Hydrology, Thakurova 7, Prague, 16629 Czech Republic
AU: Green, R
AF: NREM, University of Hawaii at Manoa, 2515 Campus Road, Miller Hall 110, Honolulu, HI 96822 United States
AU: Loo, B
AF: Hawaii Department of Agriculture, Chemical Analysis Laboratory, 2725 Waimano Home Rd., Pearl City, HI 96782 United States
AB: Intensive use of pesticides in agriculture inevitably poses an increased threat to groundwater. Recent findings of pesticide residues in selected drinking water wells in Hawaii brings further attention to this problem since the primary source for potable water in Hawaii is groundwater from basal or dike-confined aquifers. A challenging research project was carried out at the University of Hawaii to elucidate potential impacts of selected pesticides on groundwater and to understand pesticide behavior in tropical soils. The major outcome of the project will be a recommendation to the Hawaii Department of Agriculture whether to restrict or approve these pesticide products entering Hawaii's agricultural market. Three sites on Oahu, one on Maui, and one on Kauai were selected for field evaluation of leaching. The soil types on Oahu are Wahiawa Oxisol (Poamoho), Molokai Oxisol (Kunia), and Waialua Vertisol (Waimanalo). The soil at Kula, Maui is an andisol (loam of Kula series) and that at Mana, Kauai is a Vertisol of Malama series. Three herbicides (S-metolachlor, imazaquin, sulfometuron methyl), one fungicide (trifloxystrobin), and one insecticide (imidacloprid) were used in our study. In addition, a commonly used herbicide (atrazine) and potassium bromide tracer were applied as reference chemicals. After spraying, the plots were covered with straw to decrease evaporation from bare soil surface and irrigated with aerial sprinklers for a period of 16 weeks. Disturbed soil samples from various depths were taken at regular intervals for pesticide analysis. Water flow dynamics was monitored with TDR probes and tensiometers installed at three depths. Weather data were acquired simultaneously. In-situ measurements of unsaturated hydraulic conductivity were done using a tension disc infiltrometer. Laboratory experiments of soil-water retention, as well as degradation, sorption, and column displacement experiments for the selected pesticides were conducted. Hence, comprehensive a database for mathematical modeling of the pesticide transport was obtained. Results so far indicate that S-metolachlor showed its low leachability and short decay half-life. On the other hand, imidacloprid exhibited its low sorption ability with higher leaching potential and longer half-life. Likewise, transport of bromide seems to be controlled by soil hydrologic properties and water application rates.
DE: 1899 General or miscellaneous
DE: 1818 Evapotranspiration
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting